Angelo Gavezzotti
This document has been produced by scanner reproduction of the original drawings prepared for the paper:
A. Gavezzotti (1976). The two-dimensional space groups: an illustration. Atti della Accademia Nazionale dei Lincei, Anno CCCLXXIII-1976, Memorie Classe di Scienze Fisiche, Matematiche e Naturali, Serie VIII-Volume XIII, Sezione II (Fisica, Chimica, Geologia, Paleontologia e Mineralogia).
There are differences between the plane group symbols as used in the drawings and those given in the most recent version of International Tables for Crystallography (2002). Vol. A, Space-group symmetry, edited by Th. Hahn, 5th ed. Dordrecht: Kluwer Academic Publishers. In particular p, m, g and c should be italic. Moreover:
old symbol
new symbol
pmm
p2mm
pmg
p2mg
pgg
p2gg
cmm
c2mm
p4m
p4mm
p4g
p4gm
p6m
p6mm
The unit cells drawn at the top right of each diagram are not of the same size (isotropic scaling allowed), and some of the cells do not respect the orientation and proportion of the drawing. This is the case for: orientation and proportion: p1, p2; proportion: pm, cm, p2mm, p2mg, p2gg, c2mm. Some of the mirror planes appear as double lines rather than one thick single one.
The originals are in black China ink on transparent paper, which has become brittle with time. It has therefore been decided to leave the drawings as they were, without attempting corrections at the risk of permanent damage on the originals.
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p1
p2
pm
pg
cm
pmm
pmg
pgg
cmm
p4
p4m
p4g
p3
p3m1
p6
